This invention relates generally to wind turbines, and more specifically to methods and apparatus for increasing the efficiency of wind turbines.
Recently, wind turbines have received increased attention as environmentally safe and relatively inexpensive alternative energy sources. With this growing interest, considerable efforts have been made to develop wind turbines that are reliable and efficient.
Generally, a wind turbine includes a rotor having one or more blades. The rotor is mounted on a housing or nacelle, which is positioned on top of a truss or tubular tower. The turbine's blades transform wind energy into a rotational torque or force that drives one or more generators, rotationally coupled to the rotor through a gearbox. The gearbox steps up the inherently low rotational speed of the turbine rotor for the generator to efficiently convert mechanical energy to electrical energy, which is fed into a utility grid. Gearless direct drive turbines also exist.
Under some atmospheric conditions, the rotor blades become covered with ice. Ice buildup typically occurs on the leading edge of the airfoil and causes a reduced lifting capability. As the ice layer becomes increasingly thick, weight is added to the airfoil so that the lifting airfoil surface becomes modified. For air turbines, this modification can result in diminished aerodynamic rotor blade performance. (For airfoils on airplanes, a similar loss in performance can result in a crash.)
Airfoils or rotor blades can be difficult to service due to their operating environment. Installing resistive heating wires or other electrical conductors onto the leading edge of an airfoil can provide a conduit for lightning that renders the airfoil useless. In at least one known technique for reducing icing, an inflatable air bladder has been bonded to the leading edge of airfoils. However, inflation of the air bladder alters the aerodynamics of the airfoil or rotor blade, and the air bladder itself may be or become subject to fatigue and failure in at least some environments.